UC Davis Cancer Center researchers have identified a protein that may allow breast cancer to spread and make it resistant to drugs.
The research team led by Kermit Carraway have discovered a protein called Muc4, which belongs to a group of proteins called mucins, commonly found in fluids such as tears and mucus.
"Breast cancer deaths are caused by metastasis, not by the primary tumor," said Carraway.
"It's at that point that the disease also becomes difficult to treat. We think that Muc4 may be packing a one-two punch by promoting the release of breast cancer cells from the primary tumor and then inhibiting their death," he added.
During the study, the researchers conducted two experiments.
In the first experiment, they compared breast cancer cells that express Muc4 with those for which Muc4 production is blocked.
The researchers then exposed both types of cells to chemotherapy drugs and found that Muc4-producing cells survived.
In the second experiment, they compared breast cancer cells and epithelial cells that do not naturally express Muc4 but were engineered to do so.
"Our results lead us to believe that Muc4 is somehow disrupting normal links between epithelial cells," said UC Davis graduate student Heather Workman, lead author of the study.
"We now need to refine our understanding of this disruption process in order to find ways to interfere with it. There currently are no drugs that target Muc4, and this research will help change that," she added.
For further understanding, Carraway is preparing to test metastasizing breast cancer tumor cells for the overexpression of Muc4.
"If we find that Muc4 is all over metastasizing breast cancer cells, it will confirm that we are on the right track," he said.
The study appears Cancer Research.